If there are any Dutch readers here:
In the Netherlands, you can deduct an office at home as a business expense, depending on some variables that your accountant will fill you in on.
Keep in mind that all kinds of things you take for granted as an employee and consumer in the Netherlands don’t fly once you’ve become independent. You really will be on your own.
The tax office (‘belastingdienst’) and Chamber of Commerce (‘Kamer van Koophandel’) are your friends, especially the former. Visit them as they’ve got loads of useful advice. The latter will in some cases actually try and discourage you from starting a business as part of their spiel. Make sure you come across as if you mean it.
The Usenet newsgroup nl.ondernemen is NOT there to spam your fellow entrepeneurs with your brilliant product, but DOES provide a place where other entrepeneurs will listen and dispense advice. Read up in http://groups.google.com/groups?q=group:nl.ondernemen before you start posting.
Keep in mind that for several organisations that could spell big trouble for you (belastingdienst, GAK), you need to look like a business: have business cards, stationary, clients (if you rely on one major client, the GAK will conclude that you are their employee and start taxing them accordingly!), spend most of your time on the job, advertize, etc.